Endocrine Abstracts

Adrenomedullin is a vasoactive peptide which is classically produced by vascular endothelial cells. It has been identified in the rat adrenal gland where it has a zone-specific distribution, being produced by the zona glomerulosa and medulla, but not the inner zones (zona fasciculata and reticularis). There is also an extensive peptidergic innervation to the zona glomerulosa, but not to the other cortical zones.

There are several possible reasons for this distribution of peptide: the zona glomerulosa is the site of aldosterone synthesis and the major site of cell division in the adrenal. It is also the region where blood flow through the gland is controlled.

Adrenomedullin and its related peptide, PAMP, appear to have a role in each of these processes, although the role of adrenomedullin in regulating aldosterone secretion remains unresolved. These peptides have been shown to stimulate growth of adrenal H295R cells in culture. It appears that peptides synthesised by glomerulosa cells may have a paracrine action on inner zone cells. PAMP, for example, has been shown to act on the H295R cell line to increase DHEA secretion and CYP-17 expression. In an intact rat adrenal preparation both PAMP and adrenomedullin stimulate glucocorticoid secretion.

There is still much that is not understood, however, particularly regarding the regulation of peptide expression in the adrenal cortex and the role of these peptides in adrenal development.